It is known that metal-air batteries present remarkable characteristics which make them suitable for a number of important uses and that rechargeable zinc-air batteries are well known in the art. In one approach, the battery is recharged solely by application of electric current, however the zinc electrode (in practically relevant limited-electrolyte conditions), does not maintain a compact shape on repeated charge-discharge cycling, either forming zinc dendrites, which short out the cell, or the electrode undergoes zinc shape change, where the zinc tends to redistribute over the lower part of the plate with consequent capacity fading and stack deformation.
Air electrodes based on carbon bonded by polymer have limited life when exposed to the rigors of charge-discharge cycling, especially on erosive oxygen evolution on charge. The previous designs often needed also to carry an electrolyte pump, excess zinc and excess electrolyte in the battery as means to prolong cycle life, but this lowers attainable energy densities to around 100-150 Wh/kg.
In another approach, the battery is mechanically refueled by replacing spent anodes and electrolyte in the cell each cycle and recycling spent anodes back to zinc anodes off-board in a recycling process. Energy densities of 250 Wh/kg have been achieved.
Air electrodes to date have limited cycle life when exposed to the massive physical shock of replacement of zinc anodes in each cell, electrolyte leakage is difficult to prevent in such a disassembly-structured system, and again the need for excess zinc and excess electrolyte in the cell negatively impacts energy density.
To date, a high energy density zinc-air battery, with a useful minimum zinc and alkaline electrolyte quantity, which is compact and rechargeable is lacking.